Abstract

Background Screen entertainment for young children has been associated with several aspects of psychosocial adjustment. Most research
is from North America and focuses on television. Few longitudinal studies have compared the effects of TV and electronic games,
or have investigated gender differences.

Purpose To explore how time watching TV and playing electronic games at age 5 years each predicts change in psychosocial adjustment
in a representative sample of 7 year-olds from the UK.

Methods Typical daily hours viewing television and playing electronic games at age 5 years were reported by mothers of 11 014 children
from the UK Millennium Cohort Study. Conduct problems, emotional symptoms, peer relationship problems, hyperactivity/inattention
and prosocial behaviour were reported by mothers using the Strengths and Difficulties Questionnaire. Change in adjustment
from age 5 years to 7 years was regressed on screen exposures; adjusting for family characteristics and functioning, and child
characteristics.

Results Watching TV for 3 h or more at 5 years predicted a 0.13 point increase (95% CI 0.03 to 0.24) in conduct problems by 7 years,
compared with watching for under an hour, but playing electronic games was not associated with conduct problems. No associations
were found between either type of screen time and emotional symptoms, hyperactivity/inattention, peer relationship problems
or prosocial behaviour. There was no evidence of gender differences in the effect of screen time.

Conclusions TV but not electronic games predicted a small increase in conduct problems. Screen time did not predict other aspects of
psychosocial adjustment. Further work is required to establish causal mechanisms.

Introduction

Television and electronic games are prominent features of children's home environments in many high-income countries. However,
children's heavy screen time has been linked with obesity, sleep problems, lower cognitive skills and poor academic adjustment.1–3 High screen time may also predict behavioural and emotional problems in children, including aggression,4,5 anxiety and depression,5–7 victimisation,3 social isolation,8 reduced prosocial behaviour4,9 and attentional problems.4,10,11

Heavy screen time might impair children's mental health in various ways, particularly if it involves viewing material not
primarily designed for children and/or with less adult supervision. Screen entertainment's rapid pace, frequent changes of
image and capacity to excite may shorten concentration span12 and reduce time spent on other key developmental activities, including interpersonal interactions.13 Violent content may ‘prime’ children for aggression and prompt them to imitate aggressive behaviour they have just seen.
Longer term effects may include desensitisation to violence, and development of attitudes supporting the use of aggression.5,14 Violent content may also increase children's perceptions that the world is a ‘scary place’, resulting in trauma symptoms
including depression and anxiety.6

It is thought that many psychological processes associated with exposure to TV and electronic games are similar, particularly
those regarding the development of attentional problems and aggressive behaviour.15 However, games may have more powerful effects due to active user engagement, identification with characters and repeated
rehearsal and reinforcement.16 Gaming's interactive and absorbing qualities may substitute for interpersonal relationships and increase social isolation.17 Such isolation may provoke anxiety and depression,18 or, if coupled with reduced empathy (from exposure to violent games) may depress prosocial behaviour.19 Few studies have examined young children's use of electronic games, although a recent study found negative effects of television
and video game exposure on attentional problems in middle childhood.11

There are, however, a number of alternative explanations for associations observed between screen time and psychosocial adjustment.
Family circumstances and functioning may underpin variation in children's screen time and poor adjustment.20 Links between screen time and mental health may be indirect, rather than direct, for example, via increased sedentary behaviour,
sleeping difficulties and language development.21–23 Lastly, the child's own temperament may predict screen time.24 Longitudinal studies of early screen exposure on children's mental health must take account of these alternative possibilities,
in order to demonstrate direct associations between screen time and children's mental health.

More research would be valuable to supplement existing longitudinal studies on young children that do allow for a range of
confounders.3,9,10,25,26 All but one9 of these studies come from North America and findings are inconsistent with regard to attentional problems4,10,25 and aggression.3,26 There are also limitations in scope. Only two examined prosocial behaviour.9,26 Only one recent study has distinguished between TV and video game exposure,11 but did not allow for many potential confounders. None of these studies examined gender differences, although psychosocial
adjustment and screen use are patterned by gender.27–31

This study explores associations between children's screen exposure at age 5 years and change in adjustment from ages 5 years
to 7 years, using a nationally representative sample from the UK. In the UK, watching television, videos or DVDs and electronic
gaming using a games console or computer are the most common ‘media activities’ for 5–7-year-olds, and average 2011 weekly
exposure times were 15 h TV compared with 6½ h gaming.32 We explore TV/video/DVD watching separately from gaming, to see whether passive and interactive forms of screen time have
similar or different effects. We examine gender differences and take account of a wide range of confounders, to assess whether
screen exposure may be an independent predictor of children's mental health.

Methods

Participants

The Millennium Cohort Study is a prospective study of UK children born between September 2000 and January 2002 eligible for
child benefit (a universal benefit).33–37 A stratified clustered sampling design over-represented children from disadvantaged areas, ethnic minority groups and from
Wales, Scotland and northern Ireland. Families were first surveyed at 9 months, when 18 818 children from 18 552 families
were contacted (72% of eligible cases). Families were contacted again when children were aged 3 years, 5 years and 7 years.
Parents were given the opportunity to opt out, and consent was sought and obtained at each contact. The survey received ethical
approval from the South-West, London, Northern and Yorkshire Multi-centre Research Ethics Committees of the NHS.

Study sample

At age 7 years, 13 857 children remained in the survey. Survey attrition was higher in disadvantaged families, where respondents
had moved home and where consent to data linkage was not given. This study was restricted to singleton cases (N=13 681), where
the child's natural mother provided information at all four contacts (N=11 014). Sample characteristics are shown in table 1.

Outcome measures

Psychosocial adjustment was reported by mothers at ages 5 years and 7 years using the Strengths and Difficulties Questionnaire
(SDQ),38 a widely-used survey instrument with high validity and reliability. The SDQ contains five scales, measuring conduct problems,
emotional symptoms, inattention/hyperactivity, peer relationship problems and prosocial behaviour. Each scale contains five
items scored from 0 to 2, giving a scale range of 0 to 10. Change scores were calculated by subtracting age 5 years from age
7 years scores, to give measures ranging from −10 to +10.

Screen time

Television/video/DVD viewing (referred to as ‘TV’ here) and playing computer or other electronic games (referred to as ‘electronic
games’) were reported by mothers when children were age 5 years. For both types of screen time, typical weekday term-time
hours of exposure outside school were measured on a 6-point scale: none, <1 h, 1–<3 h, 3–<5 h, 5–<7 h, 7 h or more.

Covariates

Selection of covariates was guided by the literature on associations with adjustment and screen use. Sociodemographic factors
and maternal characteristics (measured when child aged 1 year unless otherwise stated) included mother's ethnicity, maternal
education, equivalised household income, maternal employment (child aged 5 years), maternal physical and mental health using
the SF-8 scale39 and family composition (biological father's presence and number of child's siblings in household, both age 5 years). Family
functioning comprised warmth and conflict in the mother-child relationship at age 3 years;40 frequency of parent-child joint activities at age 5 years (seven items); and ‘household chaos’ at age 5 years using a three-item
version of the confusion, hubbub and order scale.41 Child characteristics measured at age 5 years included researcher-assessed cognitive development (British Ability Scale picture
similarities and naming vocabulary scores42); mother's reports of limiting long-term illness or disability, sleeping difficulties (single item), physical activity (two
items) and negative attitudes to school (two items). Lastly, the relevant SDQ score at age 5 years was used to control for
prior level of each outcome measure.

Data analysis

Change in each SDQ scale from ages 5 years to 7 years was regressed separately on screen time using STATA SE12.1 (Stata Corporation,
Texas, USA). The survey option took account of the complex survey design and used longitudinal survey weights to compensate
for attrition.

Levels of missing information were at less than 2% of cases for most measures including screen exposure. Exceptions were household
income, warmth and conflict scores, and maternal education (7–14%). The overall percentage of missing data was 27%. In order
to decrease bias and increase analytical power, we used multiple chained equations (using the mi package in Stata 12) to impute
missing values43 separately by gender. Complete case analyses were performed before using imputed data sets. Since the two sets of findings
were similar, analyses using the imputed data set are presented here. Estimates were combined across 30 imputed data sets.
Cases where the outcome variable was missing (N=514, 4.7%) were excluded from analysis (but not imputation) models.43 Missing SDQ information was more likely if mothers were from ethnic minorities, less well-educated, not in work and had a
less warm relationship with their child.

Results

At age 5 years, almost two-thirds of children watched TV for between 1 h and 3 h daily, with 15% watching for ≥ 3 h (table 2). Very few (<2%) did not watch any TV. Although TV and games exposure were correlated (r=0.20, p<0.001), exposure to games
was lower: only 3% played for ≥ 3 h daily. As table 2 also shows, boys’ levels of TV and games exposure were higher than girls’.

Children's exposure to TV/videos/DVDs and electronic games at age 5 years

Information on continuous age 7 years adjustment scores are shown in table 3, and abnormal levels of problems defined using recommended cut-offs, indicative of psychiatric diagnoses.44,45 Boys were more likely than girls to show abnormal levels of problems.

Multivariable linear regression models explored associations between screen time and change in each continuous adjustment
score from ages 5 years to 7 years. These models provide more sensitive tests of associations between screen exposure and
adjustment than logistic analyses using abnormal levels of problems as binary outcomes. Separate models examined the effects
of: (a) TV only; (b) electronic games only; and (c) combined screen time. For TV and electronic games, the last three response
categories were combined due to small numbers. The reference group was exposure for under an hour daily. For combined screen
time, the lack of detailed information necessitated different groupings: 1% used neither type of screen; 18% used either or
both for less than an hour daily, but neither for an hour or more (reference group); 65% used either/both types for an hour
or more, but neither for three or more hours; and 16% used either or both for three or more hours.

First, models for screen exposure adjusted for gender, age in months at the 7 years contact and the relevant age 5 years SDQ
score (table 4). Exposure to either TV or games for three or more hours was associated with increases in all problems, and (TV only) with
reduced prosocial behaviour. Negative effects of exposure for between 1 h and 3 h daily were weaker and less consistent. Children
playing no games were more likely to show increased problems (except peer problems), compared with playing for <1 h daily.
Interaction terms for gender×TV or gender×electronic games were added (as appropriate) to these models. None was statistically
significant (p<0.05), suggesting no gender differences in the effect of TV or games on adjustment. Model C (combined screen
use) showed similar effects to the model for TV exposure.

Associations between typical daily screen exposure time at 5 years and change in psychosocial adjustment from 5 years to 7 years,
adjusting for gender, age and prior adjustment score

The next stage of modelling further adjusted for the full set of covariates relating to maternal and family characteristics;
family functioning; and child characteristics (table 5, see note listing covariates in full). All covariates had statistically significant associations (p<0.05) with one or more
outcomes in multivariable models (not shown). In models A and B, TV and games use were each modelled separately. Most associations
with adjustment were attenuated to non-significance. The only remaining statistically significant (p<0.05) association was
for TV with conduct problems. In Model A (TV modelled without electronic games use), three or more hours’ TV predicted a 0.15
point increase in conduct problems. This was reduced only slightly (to 0.13) after adjusting for games use in Model C. In
Model D, 3+ hours of either or both types of screen exposure was associated with a 0.14 point increase in conduct problems.
This corresponds to 0.09 of a SD increase in age 7 years conduct score (approximate effect size, as age 7 years scores were
not normally distributed). For problem scores (conduct, hyperactivity/inattention, emotional and peer relationship), detailed
modelling (not shown) indicated that the set of maternal and family characteristics produced the greatest reduction in the
effect of screen exposure; followed by adjustment for child characteristics. For prosocial scores, family functioning measures
produced the greatest reduction in the effect of screen exposure.

Associations between typical daily screen exposure time at 5 years and change in psychosocial adjustment from 5 years to 7 years,
with further adjustments for maternal and family characteristics, child characteristics and family functioning

Further adjustment to Models C and D in table 5 for concurrent (age 7 years) TV, electronic games or combined screen use as appropriate did not alter these findings (not
shown). No effects of concurrent exposure was statistically significant, with the exception of associations between more than
3 h TV or combined screen use at age 7 years and increased hyperactivity (coefficients respectively 0.21 95% CI 0.06 to 0.35,
p=0.005 and 0.19 95% CI 0.05 to 0.33, p=0.008).

Discussion

This study found that watching television, videos or DVDs for 3 h or more daily was associated with a small increase in conduct
problems between the ages of 5 years and 7 years, after allowing for other child and family characteristics, including parenting.
Findings are in line with other research on younger children aged 2–4 years4 and older children5 showing associations between TV exposure and aggressive behaviour and bullying; although our study was able to take account
of more potential confounders than these other studies. A third longitudinal study, with similar control variables to our
own, but with earlier exposure and a longer follow-up, did not find these effects.3 We did not find associations between electronic games use and conduct problems, which could reflect the lower exposure to
games and/or greater parental restrictions on age-appropriate content for games compared with TV.32

Negative findings for other aspects of psychosocial adjustment compared with other studies could be due to a number of reasons,
including differences in age group and follow-up period, screen exposure levels, outcome measurement and our more comprehensive
set of potential confounders. Contrary to some4,5 but not all other TV studies,3 once we had adjusted for other child and family characteristics, we did not find high levels of TV exposure predicted emotional
symptoms. This might reflect differences in age group, although TV viewing time in the other studies appears similar. The
study with negative findings3 most closely resembles our own in terms of adjustment for confounders: studies with positive findings allowed for demographic
information only46 or a more limited set of family characteristics and functioning.4 Unlike several US studies of younger and older children,4,10,11 we did not find strong evidence for effects of TV or electronic games use on attentional problems. Associations in our study
between concurrent TV and increased hyperactivity/inattention may plausibly reflect reverse causation, with active selection
of TV by the child.47 Although differences in screen time between the US studies and our own were not clear-cut, there are differences in age group
and more limited adjustment for confounders in the US studies. Not all research has supported a link between exposure time
and attentional problems,25 which may be related specifically to non-educational or very early viewing.9,48 We also did not find clear associations between screen use and peer relationship problems or prosocial behaviour, in contrast
to other research on young children. This might reflect different measures: peer relationship problems measured in our own
study constitute a broader category than victimisation, associated with TV use in a North American study.3 Two studies finding effects of TV on prosocial behaviour4,9 had different measures and did not adjust for the same range of confounders as our own study. Lastly, and despite finding,
in line with other studies,27–31 that there were gender differences in psychosocial adjustment and screen use, there was no evidence of differences between
boys and girls in the effect of screen use on adjustment.

Limitations of the study include reliance on mothers’ reports of adjustment and screen time, but the extent and direction
of any effects on our findings are uncertain. Although mother-reported screen time has been used in many other population
studies, concerns over reliability and validity have not been extensively addressed.49 In the UK, there are no guidelines on screen time for young children, unlike US and Australian public health recommendations
of less than 2 h a day.50,51 With the available measures it was not possible to look at the effects of exceeding this limit, although it was possible
to examine the 1 h limit for 3–7-year-olds called for in a recent review.52 There was also no information on weekend use, or the content or context of early screen time. Other research has indicated
the importance of content for aggression and attentional problems in young children.5,14,48 Screen time in the context of parental restrictions or discussion of content may moderate negative effects.53 However, a recent UK study pointed to limited parental restrictions on age-inappropriate material coupled with high levels
of bedroom TV and gaming devices in 5–7-year-olds.32

The main strength of this study is that it is the first in the UK to examine longitudinal associations between screen exposure
and change in psychosocial adjustment. However, further work on data with additional time points is required to establish directional
effects and causal mechanisms. Previous UK research in this field has been cross-sectional, with mixed findings.21,54,55 Other strengths include the use of observational, rather than experimental, data collected from a nationally representative
survey. The rich data set allowed for control of many important covariates related to child, maternal and family characteristics
and family functioning.21,54,55 While direct predictive effects of screen exposure time on adjustment appear to be either small or not found, it remains possible that
other effects were mediated by various child characteristics that we controlled for, or were concealed through confounding
with, for example, social patterning of screen use.

The study highlights the need for more detailed data to explore risks of various forms of screen time, including exposure
to screen violence. In addition, studies should further examine the associated child and family characteristics which appear
to account for most of the simple associations between screen exposure and psychosocial adjustment. Our findings do not demonstrate
that interventions to reduce screen exposure will improve psychosocial adjustment. Indeed, they suggest that interventions
in respect of family and child characteristics, rather than a narrow focus on screen exposure, are more likely to improve
outcomes. However, the study suggests that a cautionary approach to the heavy use of screen entertainment in young children
is justifiable in terms of potential effects on mental wellbeing, particularly conduct problems, in addition to effects on
physical health and academic progress shown elsewhere.3

Acknowledgments

We would like to thank all of the Millennium Cohort Study families for their cooperation. We are grateful to the Centre for
Longitudinal Studies (CLS), Institute of Education for the use of these data and to the Economic and Social Data Service (ESDS)
for making them available. The authors thank Geoff Der for statistical advice.

Footnotes

Contributors AP conceived the study, analysed the data and wrote the first draft. HS, DW and MH contributed to the design and interpretation
of the findings, and helped revise the article.

Funding This research was funded by the United Kingdom Medical Research Council, grant U130031238. The Millennium Cohort Study is
funded by grants to Professor Health Joshi, Director of the study, from the Economic and Social Research Council and a consortium
of government funders.

Open Access This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0)
license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative
works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/